The present invention relates generally to rotary hand tools, and, more specifically, to a high speed automatic sander which is reversible, so as to be capable of selective rotation of the sanding head in either of the clockwise or counter-clockwise directions.
Conventional rotary power sanders such as that shown in FIGS. 5 and 6 herein have been provided only with the capability of rotating the sanding disk in one direction, clockwise, from the point of view of the user of the device. While rotary power sanders have many various applications, including numerous uses in and around the home, the present invention is particularly directed toward industrial uses where especially high speeds of rotation and long periods of use may be required.
One of the more frequent uses of high speed rotary sanders is in the automobile industry, especially in the area of automobile body repair, including surface preparation and finishing. An unfortunate drawback of the unidirectional rotation of known power sanders is particularly apparent in this field. Specifically, the raw surface of the metal and each coat of paint on an automobile, whether new or refurbished, must be sanded before application of the next coat of paint, in order to ensure proper adhesion of the outermost coat and optimal appearance of the final product. Of course, rotary sanders, by their very nature, tend to throw debris accumulated from the sanded surface off the sanding disk as a surface is worked.
The dust and debris is kicked off the wheel or disk at high velocity, and thus with a significant amount of force. Accordingly, anything which is impacted by the flying debris (which may include paint chips and metal slivers) may be scratched, gouged or otherwise marred. For example, automobile windows may be damaged by flecks of material kicked from the disk of a rotary sander being used on an adjoining piece of metal. Likewise, a person positioned within the path of the flying debris may of course be injured, either by being struck by pieces of paint or metal moving at high velocity, or by inhaling from the stream or cloud of dust produced by the sanding action.
Thus, it is desirable to be able to control the direction in which the sanding disk rotates, and thereby control the direction in which the resultant debris is thrown from the disk, relative to the position of the object being sanded and to the position of the user. Frequently, in attempting to so control the flow of dust, or similarly to control the direction of disk rotation for a specific effect on the workpiece, the power sander user is forced to assume a position which is at least uncomfortable, and perhaps even dangerous. Working for extended periods of time with the body twisted into an awkward position can result in long term physical problems, as well as increased fatigue and possible mistakes and accidents in the short run.
The capability of switching rotational direction is also of great assistance when proper access to the work-piece to obtain satisfactory results can otherwise only be obtained by forcing the worker to use his or her non-dominant hand or to otherwise work in an awkward position, with the obvious consequences of decreased efficiency, increased fatigue, and possible decrease in finished work quality.
Although reversible motors are known for use in other hand-held power tools, such as commercially available drills and screwdrivers, they have not heretofore been successfully incorporated into high-speed rotary power sanders. Rather, any attempt at using such a known motor in reversible rotary power sander would have been unsatisfactory because in the reverse mode of operation the hub of the sander would become loose, and could literally fly across the room, with obvious dangerous consequences.
Thus it is an object of the present invention to provide a rotary, high-speed, power sander which can be selectively adjusted so that the sanding disk revolves either in a clockwise or counterclockwise direction.
It is further among the objects of the present invention to provide a sander having the features mentioned which can be powered, inter alia, by known pneumatic power means.
It is also among the objects of the present invention to provide a sander having the features discussed which can be operated in a safe manner, without risk of portions of the sander becoming loose and possibly airborne during use.
Accordingly, in furtherance of the above objects, the present invention is, briefly, a reversible rotary sanding power tool of the high speed, hand-held type. The tool includes a tool body, a tool head rotatably mounted on the tool body and adapted for replaceably retaining an abrasive disk, and a reversible, high-speed motor within the tool body and to which the tool head is rotatably coupled so as not to become accidentally disengaged upon operation of the power tool in either of the normal or reverse modes of operation.
The invention is also the tool described above, wherein the reversible, high-speed motor has a rotor shaft having an end which extends forwardly from the tool body for rotatably coupling to the tool head. Furthermore, the end of the rotor shaft is externally threaded and the tool head has a hub which is correspondingly internally threaded to thereby engage the end of the rotor shaft of the high-speed reversible motor.
The invention is also, briefly, the above-described tool wherein the end of the rotor shaft is hollow and has a threaded internal side wall. The tool head has a pad holder having a counterbored opening and a cap screw having a threaded shaft which corresponds to the threaded internal side wall of the rotor shaft end to thereby connect the pad holder to the high-speed reversible motor.
Also, the tool head includes a jam nut having a rearwardly disposed angled face and which is internally threaded so as to threadably engage the external threads of the rotor shaft end. The hub of the tool head has a forwardly sloped shoulder having an angle which matches that of the angled face of the jam nut, to thereby permit tight-fitting engagement of the jam nut against the shoulder of the hub when both the hub and the jam nut are disposed in their working positions on the rotor shaft end.
Also in the invention, the hub has a continuous internal side wall which defines an opening and the pad holder has an exterior side wall which corresponds in size and shape to the opening defined by the internal side wall of the hub for interlocking engagement of the hub and the pad holder in such manner that the hub and the pad retainer cannot slip circumferentially in relation to each other when under rotational force from either of the clockwise and counter-clockwise directions.
Other objects will be in part apparent and in part pointed out hereinbelow.